Field of the Invention
This invention relates to electric current collection systems, comprising a continuous live conductor, a shield enclosing the continuous live conductor, and contact segments extending through the shield in a row extending along the length of the continuous live conductor and resiliently mounted so as normally to be electrically isolated from the continuous live conductor and from each other but adapted to co-operate with a current collecting device running along the row to make electrical contact with an external contact surface of each segment in succession and displace the segment to bring an internal contact surface afforded by it into electrical connection with an internal contact surface afforded by the continuous live conductor.
According to one aspect of the present invention each segment includes a bar portion affording its internal contact surface and extending through the shield in a direction substantially perpendicular to the length of the live conductor and to the direction of displacement of the segment.
Whilst the invention is particularly applicable to a live conductor assembly mounted on the ground and engaged by a current collector pressing downwards on it, it is not necessarily limited thereto. Thus the current collector may press sideways or upwards against the live conductor. For convenience, however, references herein to upper and lower parts will be made assuming that the current collector is mounted above and presses down on the live conductor assembly.
Since the engagement between the internal contact surfaces is in the nature of a butt contact it is important that one or each surface should be capable of yielding, so as to avoid damage if the collecting device is a little too close to the live conductor, or failure to make contact if it is a little too far away.
Thus in one form of the invention the segments are resilient so that the internal contact surface of a segment engaging the continuous live conductor is free to yield resiliently relatively to the external contact surface engaging the current collector.
The external contact surface for engagement by a current collector may extend obliquely across the direction of movement of the collector. Thus one form of segment is formed of wire generally in the form of a `Z` and bent so that the ends penetrate the sides of the shield to make contact with the live conductor while the middle limb extends obliquely across the top of the shield to be engaged by the current collector. Successive segments preferably overlap longitudinally so that a current collector member extending transversely across the shield will engage two or more segments simultaneously.
For applications such as tramways or street cars the shield is preferably accommodated in a trough which is sunk flush into the roadway and has overhanging sides forming a top with a narrow slot in it through which the row of contact segments is accessible, and the row of contact segments together with the adjacent portion of the shield have their upper surface flush with the top of the trough and virtually fill the slot.
In one form of the invention each segment comprises a straight rod extending transversely through the shield with its ends projecting to form a pin rack and which includes a current collecting device comprising a pinion affording sprockets meshing with the said rack, and providing the external contact surfaces.
According to another aspect of the invention an electric traction current collection system for a vehicle comprises a continuously live conductor, a shield enclosing the continuously live conductor, and contact segments extending through the shield in a row extending along the length of the continuously live conductor and resiliently mounted so as normally to be electrically isolated from the continuously live conductor and from each other, and a current collecting device carried by the vehicle and adapted to run along the row to make electrical contact with an external contact surface of each segment in succession and displace the segment to bring an internal contact surface afforded by it into electrical connection with an internal contact surface afforded by the continuously live conductor, in which the current collecting device comprises an electrically driven pinion and the segments extend through the insulating sheath and afford conducting teeth projecting so as to provide the external contact surfaces and to form a rack meshing with the driving pinion to effect a positive rack and pinion drive. Again each segment conveniently includes a straight rod extending transversely through the shield.
Preferably each segment is formed integrally in a single piece, for example from round rod material.
The internal contact surface of the continuously live conductor may be free to yield relatively to its support. Thus, the conductor may include a multiple strand, helically wound cable, either of hollow tubular form, or provided with a core of rubber or like resilient material, or a helical metal spring.
Conveniently the major part of the shield is formed by a member, referred to for convenience as a tyre, which is of resilient insulating rubber-like material of arch section, for example of truncated inverted V form.
Alternatively the system may include a pair of continuously live conductors, the segments being supported on a web of rubber or like resilient material located between the two live conductors.
If desired the portion of the shield remote from the contact segments may comprise a rigid base affording rails on surfaces remote from the shield, the current collector including reaction wheels running on such rails to control the extent to which the current collecting wheels displace the segments towards the continuously live conductor.